@luh-divvy Reactivity0
Your plutonium application is out of date.
Solution: Find and run the file "plutonium.exe" on your computer.
After that run your launcher file again ("plutonium-launcher-win32.exe") and the error code should disappear. You'll be able to login & resume playing.
If you can't find the files, install the software "Find Everything" (https://www.voidtools.com/) and search "plutonium" instead of using file explorer